In present-day cone-beam X-ray devices available on the market, a three-dimensional radiograph of a volume is generated for the creation of dental 3D radiographs of the jaw and head region of a patient. The volume is determined as to position and size by the operation of positioning the patient relatively to the apparatus, the selection of the rotational movement of the X-ray emitter and the X-ray detector around the patient, and the adjustment of other variables such as the aperture size, beam geometry, etc.
The problem confronted by the dentist is to preselect the position and/or the size of the volume such that the volume recorded coincides with the region of medical interest. The complexity of this problem increases as the size of the volume to be examined decreases. For this reason, various positioning aids are made available to the operator, these being mostly based on mechanical or optical methods such as monitoring the positioning by means of a light-beam localizer on the patient's head.
DE 10 2004 020 370 A1 discloses an X-ray apparatus in which an optical camera is provided on an X-ray emitter for creating an optical image of the patient's head being X-rayed by said emitter. An optical image can be created at the start of, or during, the rotation of the X-ray emitter around the patient's head in order to facilitate the formation of an association between the radiograph and the visible surface of the object being X-rayed, for diagnostic purposes.